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Pneumatic Brushless DC-Electric [EC] DC-Electric with integrated clutch Volume High High Low Compressed air
used Yes No No Multiple torque
and speed requirements with "change on the fly" capability
and/or speed control No Yes No Budget Low High Low |
Selecting a Power
Screwdriver looks like a simple task, but how often does this seemingly “simple” task or “easy” application turn
out to be more complex than anticipated? This selection guide should give
some insight as to the different considerations that should be given when
selecting a handheld power screwdriver to be used for mass production. Since this
How-to-Guide is for high-volume production at industries, which require a
high level of accuracy and precision, industrial tools such as impact
wrenches, slip-clutch tools or stall tools are not being considered. Tool Considerations First and foremost,
a decision should be made in regard to the drive-medium of the desired power
screwdriver. Generally, there are two major drive mediums: Pneumatic or
Electric (either DC-brushless or DC with clutch). The decision to use
one over the other, is generally guided by the following criteria (in no
particular order): Volume A pneumatic motor is extremely durable and can
be stressed to a full standstill; it also tolerates a negative turn-direction
even if the load is increased! This is still one of the historic advantages
of a pneumatic motor, if the air going into this motor is dry, clean and
lubricated. Under such conditions a pneumatic screwdriver can perform up to
2-Million cycles without the need for maintenance. If non-lubricated, but dry
and clean air is used, the number of cycles will drop, but is then still about
equal to a DC-electric tool with integrated clutch. For large production volumes, the use of a
pneumatic Screwdriver or a brushless DC-electric (EC) Screwdriver is
recommended. For areas, where only small production runs are required, a
handheld Electric Screwdriver (DC with integrated clutch) is recommended. Air available? Compressed air is without a doubt more expensive than electricity, since in most cases it takes an electric motor to produce the compressed air. Consideration should be given to the fact that not 100% of the electric energy is transferred to the rotating shaft of an electric motor. Another important issue to consider is that a pneumatic tool does not really “mind” air-pressure fluctuations and screwdrivers equipped with a Micromat®- or Minimat®-clutch will remain highly accurate as long as there is sufficient air for the clutch to shut-off. An electric screwdriver is more sensitive and may react adversely to fluctuating power by shortening out. The maximum allowable power fluctuation for DC-tools is generally only +/- 10%. Naturally, if no shop-air is available, the use
of an Electric Screwdriver (any kind) is necessary. Multiple
torque-stages; changing torque on the fly; speed control At stations where one screwdriver has to perform
assemblies that require multiple torque-settings, the best solution is a
brushless DC-electric screwdriver (transducerized or not) with a Controller. This allows a direct input of the required
torque value. The
controllers are also able to store comprehensive
screwdriving-programs, which can include different torque-stages, angular
displacement of fastener, torque-HOLD (compensation for joint relaxation),
high speed for run-down and low-speed for shut-off, etc. |
Budget
considerations When
considering the spending budget, the following rough cost guidelines for
power screwdrivers apply -
A handheld electric screwdriver (DC with
integrated clutch) is generally less expensive or equal to the cost of a
handheld pneumatic screwdriver. -
A pneumatic screwdriver is always less expensive
than a brushless DC-electric screwdriver (EC) and is easier to install and
maintain. -
A brushless DC-electric screwdriver offers the
most flexible solution with corresponding pricing. Commonality There
are several common features that should be considered when selecting a
handheld Screwdriver; they are: -
High torque accuracy -
Low noise level -
Light weight -
Slender with non-slip grip -
Ergonomic housing made to fit the
hand -
Low air-consumption rates -
Highly durable Special Application
Requirements Here
are some application examples with screwdriver recommendations:
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